Air filter



C. A. CAMPBELL Oct. A25, 1938.

AIR FILTER Filed June 26, 1957 Emma @DDE @EEE @DDE @EEE @DDE DDE 1 :inventor @a/f0.5 QLQQMMP-be' I Gttornegs Patented Oct. 25, 1938 UNITEDV 'STATES PATENT OFFICE ration of New Jersey Application June 26, 1937, serial No. 150,617

3 Claims.

This invention relates to air lters, and particularly filters used to protect automatic valves of railway air brakes (such for example as triple valves, vent valves, applicationvalves, etc.) from dust, scale and other abrasive substances which enter the brake pipe.

A familiar example is the annular cylindrical lter mounted in the pipe bracket ofthe AB freightbrake now standard on American rail- 10. ways. This is interposed between the brake pipe on the one hand, and the piston chambers of the service and emergency portions of. the AB valve on the other.

As is well known, brake pipe pressures are substantial, and although the lter is protected against undue pressure differentials by so-called H by-pass check valves, it must be of rugged construction, and proof against leakage even under shock pressures which sometimes occur.

The present invention offers a successful solution of this problem' and -will be described as used in conjunctionwith the AB brake.

In the drawing,-

Fig. 1 is a section through the pipe bracket of the AB brake, the section being taken on the axis of the filter chamber characteristic of this bracket. The improved filter element is shown in place and in longitudinal axial section.

Fig. 2-r is a longitudinal axial section of the iilter cartridge, partially assembled.

Fig. 3 is an end elevation of the cartridge parti in section.

Fig. 4 is a fragmentary perspective of the main filtering element.

' The main ltering element comprises a zigzag sustaining member of stiff heavy woven wire (preferably hard brass) indicated generally by the numeral 5, and an outer covering of filtering material, preferably wool felt, indicated generally by the numeral l1. The two are in the form of strips each longer than it is wide, the woven Wire strip vbeing slightly wider than the felt strip to afford; stock for clamping the edge of the felt.

The clamped edge is best shown in Fig. 4. The woven wire is folded inward \on itself at 8, and then outward at 9 to clamp the infolded edge I I of. the felt. The woven wire and felt are thus clamped together along both long edges. They are then folded into the zigzag or star form, indicated in Figs. 3 and 4, with the felt on the outer side. The felt extends beyond the woven wire at one end and this extending end is stapled into the reentrant angle as indicated at I2, forming a close joint.

No novelty is here claimed for the filter ele- (Cl. 18S-'11) ment above described, nor is the invention limited to the specilic method of forming such element.

Such an element, or its approximate equivalent, is inserted between a central tube I3 and an outer tube I4, each preferably formed of seamless 5 bra-ss tubing. These tubes are each perforated, as indicated at I5 and I6, respectively, throughout their circumferences and for distances commensurate with the axial length of the zigzag lter element. Eachend of each tube I3 and 'I4 10 is'formed with projecting fingers I1 and I9.

To seal the ends of the filter element an annularv washer I9 of felt is placed against each end and closely fills the interval between the inner and outer tubes I3 and I4. Over these are placed suc- 15 cessively a brass Washer or plate 2I and a second felt Awasher 22, both of which are substantially coextensive with felt washer I9 and the end of the zigzag filter'element. Then the ngers Il are bent outward and the lingers I8 inward to 20 retain the edges of the outer felt washers 22 and to exert suficient pressure through these edges on washer 2l to produce tight engagement between washers I9 and the zigzag lter.

In Fig. l a portion of. the pipe bracket is indi- 25 cated at 23. The annular space 24 within the surrounding casing is in direct communication with the brake pipe.

The felt washer 22 at one end of the lter cartridge, seats tightly against the annular rib or 30 ridge 25, and that at the other end tightly engages a 'similar rib 26 on the adjustable and removable plug 21 threaded into the bracket. The passage 128 leads to the piston chamber of the service portion while the small port 29 offers communication to the piston chamber of the emergency portion.

Thus a filter element of large effective surface is interposed between the brake pipe and the mechanism of the brake valve and precludes the entrance of abrasive dust into the valve parts.

The rigid metal washer or plate 2I- has a very important function. It distributes the annular, line sealing pressurevof narrow ribs 25 and 26 and the pressure of fingers4 I1 and I8 over the entire end areas of the zigzag filter element, 4 thereby ensuring a close seal between the entire end areas of. that element and the coextensive felt washer I9. Metal Washer 2| also forces felt washer 22 into good sealing engagement with ribs 25 and 25. I 50 In this way leakage past the ends of the filter element and the cartridge is effectively prevented.

What is claimed is,- 1. An annular lter cartridge intended to be mounted in a filter casing and to seal tightly at? 6 its ends with annular ribs on the casing, comprising in combination, a longitudinally rigid illter element of generally annular form; compressible gaskets overlying the ends of said element and substantially coextensive therewith: load pressure distributing plates overlying said gaskets and also approximately coextensive with the ends of said filtering element; gaskets overlying said plates and capable of sealing with said ribs, the ribs being relatively narrow as compared with said pressure distributing plates; and means for holding the above-named parts in assembled relation.

2. An annular lter cartridge intended to be located in a illter casing and to seal tightly at its ends against annular ribs on the casing, comprising in combination, a longitudinally pleated filter element made up of a iiltering fabric and a foraminous metal stiifening core; inner gaskets overlying the ends of said element and coextensive with said pleats to eiect a seal over the entire ends of the pleats; annular pressure distributing plates overlying and coextensive with said gaskets; outer gaskets overlying said plates and adapted to be engaged by said ribs, the ribs being relatively narrow as compared with said plates; and means comprising a foraminous shell arranged to hold the above named parts in assembled relation, the parts being so arranged that in service the outer gaskets seal the plates to the ribs, and the plates and inner gaskets seal over the entire end area of the lter element whereby a close seal is secured and the core is protected from local deforming stresses.

3. The combination in-a lilter including a casing having a chamber provided with annular sealing ribs and a uid inlet and a :fluid outlet, of a longitudinally rigid lter element of generallyannular form with longitudinally extending, open-end pleats located in said chamber; annular inner gaskets of compressible material overlying and completely sealing the open ends of said pleats; rigid, annular, pressure distributing plates overlying said gaskets and substantially coextensive therewith; and'annular outer gaskets overlying said plates, said sealing ribs on the casing being relatively narrow as compared with said plates and having tight sealing engagement with said outer gaskets so that said pressure distributing plates maintain said inner gaskets in close' sealing contact with the ends of the lter element and all fluid owing between said inlet and outlet isfcompelled to pass through the lter element.

CHARLES A. CAMPBEIL. 

